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The formation of fissures in the concrete cover above the reinforcement bars represents a preferential pathway for the ingress of water and aggressive agents such as CO 2 (lowering of pH around the rebar) and chloride anions (pitting corrosion) into concrete. The physical formation of cracks therefore favors the chemical degradation of concrete ...
When it reacts with concrete, it causes the slab to expand, lifting, distorting and cracking as well as exerting a pressure onto the surrounding walls which can cause movements significantly weakening the structure. Some infill materials frequently encountered in building fondations and causing sulfate attack are the following: [2] Red Ash
The chemical processes of Portland cement hydration lead to another type of shrinkage, called the autogeneous shrinkage, which is observed in sealed specimens, i.e., at no moisture loss. It is caused partly by chemical volume changes, but mainly by self-desiccation due to loss of water consumed by the hydration reaction.
The cracking caused by ASR can have several negative impacts on concrete, including: [20] Expansion: The swelling nature of ASR gel increases the chance of expansion in concrete elements. Compressive strength : The effect of ASR on compressive strength can be minor for low expansion levels, to relatively higher degrees at larger expansion.
Exfoliated granite sheets in Texas, possibly caused by pressure release. Pressure release or unloading is a form of physical weathering seen when deeply buried rock is exhumed. Intrusive igneous rocks, such as granite, are formed deep beneath the Earth's surface. They are under tremendous pressure because of the overlying rock material. When ...
Pyrite oxidation is sufficiently exothermic that underground coal mines in high-sulfur coal seams have occasionally had serious problems with spontaneous combustion. [47] The solution is the use of buffer blasting and the use of various sealing or cladding agents to hermetically seal the mined-out areas to exclude oxygen.
A high proportion of damp problems in buildings are caused by ambient climate dependent factors of condensation and rain penetration. [1] Capillary penetration of fluid from the ground up through concrete or masonry is known as "rising damp" and is governed by the shape and porosity of the construction materials through which this evaporation ...
High-pressure chemistry is concerned with those chemical processes that are carried out under high pressure – pressures in the thousands of bars (100 kPa) or higher. High-pressure processes are generally faster and have a higher conversion efficiency than processes at ambient pressure.